• Proceedings of the IEEK Conference
• /
• 2004.06a
• /
• pp.151-154
• /
• 2004

In this paper. we present the 2.4 GHz and 5 GHz dual band antenna for a multiple PCB (Printed Circuit Board) antenna. Using antenna has a monopole structure with lines on FR-4(${\varepsilon}_r\;{\approx}\;4.6$) PCB. The obtained antenna can perform in 2.4 GHz and 5 GHz bands and be adopted for other wireless applications.

• The Journal of the Acoustical Society of Korea
• /
• v.17 no.5
• /
• pp.35-41
• /
• 1998

본 논문에서는 다중 빔을 사용한 저궤도 위성 이동 통신시스템 환경에서 부호 분할 다중접속 및 주파수 분할 다중접속 방식의 채널 용량을 비교 분석하였다. 위성 중계기의 출 력의 효율성, 주파수 효율성, 부호화 방식 및 안테나의 EIRP나 G/T형태 등과 같은 파라미 터들을 순방향 링크와 역방향 링크에서 채널 용량을 결정하는 시스템 파라미터로서 고려하 였고, 피더 링크(feeder link)는 Ku-band를, 사용자는 링크는 L-band를 사용한 다중 스팟빔 (spot beam) 시스템을 채널 용량 분석의 모델로 적용하였다. 분석결과 도플러 현상 및 다중 경로에 강한 부호 분할 다중접속 방식이 용량면에서 주파수 분할 다중접속 방식에 비해 성 능이 우수함을 알 수 있었다.

• Journal of The Korean Astronomical Society
• /
• v.38 no.2
• /
• pp.23-31
• /
• 2005

CN and CH band strengths for fourteen bright giants in the globular cluster M71 have been measured from archival spectra obtained with the Multiple Mirror Telescope. Adding the collected. data from the literature we confirm a bimodality of CN distribution on the red giant branch and the honzontal branch, and CN-CH anti-correlations on the lower giant branch and horizontal branch. However a CN-CH anti-correlation on the upper red giant branch is not quite clear as those of other branches. The small number If statistics could not be excluded as a possible cause. To confirm this, a greater number of sample stars are needed. We also confirm that the ratio of CN-strong to CN-weak stars is quite different from that in 47 Tuc, although the anti-correlation between CN and CH bands, the bimodality of the CN distribution, and the spatial distribution of CN stars in M71 are found to be similar to those III 47 Tuc.

• Journal of The Institute of Information and Telecommunication Facilities Engineering
• /
• v.8 no.3
• /
• pp.111-115
• /
• 2009

Cognitive Radio (CR) technology is proposed for using the unused spectrum band efficiently because of the spectrum scarcity problems. Spectrum sensing is one of the most challenging issues in cognitive radio system. In this paper, we focus on the signal detection of WiBro system band. As most of the modulated signals can be treated as cyclostationary random process, we can detect the signal of the OFDM signals in WiBro system. OFDM symbols using WiBro system have several pilot subcarriers and periodic pilots have cyclostationary characteristic. To improve the detection performance, we get diversity gain using multiple antennas.

• Proceedings of the KIEE Conference
• /
• 1987.07b
• /
• pp.894-897
• /
• 1987

Listener echos, which arise in multiple 4-wire loop connections(MLC) during the evolving switched telephone network, impare voice-band data signal transmission performance. This paper first shows the calculation method of the total number of listener echo loops over N 4-wire physical loops and presents the additative law for listener echos. It next demonstrates that about 4 dB should be ensured to Eke the transmission loss of intraoffice call path be minimum for the voice-band data service in a digital local switch.

• 한국정보통신설비학회:학술대회논문집
• /
• 2003.08a
• /
• pp.25-28
• /
• 2003

본 논문은 Ka 밴드(26.5GHz-40GHz)를 사용한 양방향 멀티미디어 시스템의 설계에 대해서 다루고 있다. 우선 무궁화 3호 위성을 이용한 시범사업의 구성 및 운영과정에 대해서 개괄하고, 시범운영에서 발견된 문제점을 소개한다. Ka 밴드 양방향 위성 시스템은 MF-TDMA(Multi-Frequency Time Division Multiple Access) 방식을 사용하여 최대 전송속도 2Mbps 이상이고, QOS(Quality of Service) 제공 등 다양한 기능을 갖추고 있으나 Ka 주파수 특성상 그 안정성에 있어서 어려움을 갖고 있다. 강우감쇄 및 전송 지연 등의 현상들을 소개하고 향후 위성 양방향 시스템의 구성과 응용 서비스를 구현할 때 고려해야 할 사항들에 대해 고찰해 보고, 해결방안을 제시하였다.

• Proceedings of the IEEK Conference
• /
• 2002.07b
• /
• pp.751-754
• /
• 2002

This paper introduces a way to realize biquadratic transfer functions using Operational Amplifiers (OAs) and Operational Transconductance Amplifiers (OTAs). The basic circuit configuration is constructed with two OAs and five OTAs. It is shown that low-pass, band-pass, high-pass, band-stop and all-pass transfer functions can be realized by suitably choosing the input terminals. And the circuit parameters can also be set by the transconductance gains of the OTAs independently. An example is given together with simulated results by PSPICE.

• ETRI Journal
• /
• v.39 no.2
• /
• pp.245-254
• /
• 2017

In-band full-duplex (IFD) communication has recently attracted a great deal of interest because it potentially provides a two-fold spectral efficiency increase over half-duplex communications. In this paper, we propose a novel digital self-interference cancelation (DSIC) algorithm for an IFD communication system in which two nodes exchange orthogonal frequency-division multiplexing (OFDM) symbols. The proposed DSIC algorithm is based on the least-squares estimation of a self-interference (SI) channel with block processing of multiple OFDM symbols, in order to eliminate the fundamental and harmonic components of SI induced through the practical radio frequency devices of an IFD transceiver. In addition, the proposed DSIC algorithm adopts discrete Fourier transform processing of the estimated SI channel to further enhance its cancelation performance. We provide a minimum number of training symbols to estimate the SI channel effectively. The evaluation results show that our proposed DSIC algorithm outperforms a conventional algorithm.

• Applied Microscopy
• /
• v.45 no.2
• /
• pp.52-57
• /
• 2015

Bulk metallic glass (BMG) shows higth strength, high elastic limit, corrosion resistance and good wear resistance and soft magnetic properties and has been considering as a candidate for new structural materials. But they show limited macroscopic plasticity and lack of tensile ductility due to highly localized shear deformation, which should be solved for real structural application. In this paper researches on the enhancement of plasticity of BMG were reviewed briefly. Introducing heterogeneous structure in glass is effective to induce more shear transformation zones (STZs) active for multiple shear band initiation and also to block the propagating shear band. Several methods such as BMG alloy design for high Poisson's ratio, addition of alloying element having positive heat of mixing, pre-straining BMG and variety of BMG composites have been developed for homogenous distribution of locally weak region, where local strain can be initiated. Therefore enhancement of plasticity of BMG is normally accompanied with some penalty of strength loss.

• Journal of the Korean Institute of Telematics and Electronics S
• /
• v.36S no.12
• /
• pp.27-33
• /
• 1999

A wavelet based multiresolution watermarking method using the human visual system (HVS) is proposed, in which a different number of watermarks, in proportion to the energy contained in each band, are embedded into each band. Experiments with various test images show that the proposed three-level wavelet based method is robust to various attacks such as joint photographic experts group (JPEG) compression, smoothing, cropping, collusion, multiple watermarking, and so on.